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                    Recover捕获异常
            
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                    示例: Bit数组
            
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                    封装
            
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                    接口
            
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                    接口是合约
            
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                    接口类型
            
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                    sort.Interface接口
            
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                    http.Handler接口
            
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                    error接口
            
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                    示例: 表达式求值
            
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                    类型断言
            
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                    基于类型断言识别错误类型
            
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                    通过类型断言查询接口
            
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                    类型分支
            
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                    示例: 基于标记的XML解码
            
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                    补充几点
            
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                    Goroutines和Channels
            
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                    Goroutines
            
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                    示例: 并发的Clock服务
            
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                    示例: 并发的Echo服务
            
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                    Channels
            
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                    并发的循环
            
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                    示例: 并发的Web爬虫
            
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                    基于select的多路复用
            
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                    示例: 并发的目录遍历
            
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                    并发的退出
            
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                    示例: 聊天服务
            
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        <li class="chapter " data-level="1.10" data-path="../ch9/ch9.html">
            
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                    基于共享变量的并发
            
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                    竞争条件
            
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        <li class="chapter " data-level="1.10.2" data-path="../ch9/ch9-02.html">
            
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                    sync.Mutex互斥锁
            
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                    sync.RWMutex读写锁
            
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                    内存同步
            
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                    sync.Once惰性初始化
            
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                <a href="../ch9/ch9-06.html">
            
                    
                    竞争条件检测
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.7" data-path="../ch9/ch9-07.html">
            
                <a href="../ch9/ch9-07.html">
            
                    
                    示例: 并发的非阻塞缓存
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.8" data-path="../ch9/ch9-08.html">
            
                <a href="../ch9/ch9-08.html">
            
                    
                    Goroutines和线程
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.11" data-path="../ch10/ch10.html">
            
                <a href="../ch10/ch10.html">
            
                    
                    包和工具
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.11.1" data-path="../ch10/ch10-01.html">
            
                <a href="../ch10/ch10-01.html">
            
                    
                    包简介
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.2" data-path="../ch10/ch10-02.html">
            
                <a href="../ch10/ch10-02.html">
            
                    
                    导入路径
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.3" data-path="../ch10/ch10-03.html">
            
                <a href="../ch10/ch10-03.html">
            
                    
                    包声明
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.4" data-path="../ch10/ch10-04.html">
            
                <a href="../ch10/ch10-04.html">
            
                    
                    导入声明
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.5" data-path="../ch10/ch10-05.html">
            
                <a href="../ch10/ch10-05.html">
            
                    
                    包的匿名导入
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.6" data-path="../ch10/ch10-06.html">
            
                <a href="../ch10/ch10-06.html">
            
                    
                    包和命名
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.7" data-path="../ch10/ch10-07.html">
            
                <a href="../ch10/ch10-07.html">
            
                    
                    工具
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.12" data-path="../ch11/ch11.html">
            
                <a href="../ch11/ch11.html">
            
                    
                    测试
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.12.1" data-path="../ch11/ch11-01.html">
            
                <a href="../ch11/ch11-01.html">
            
                    
                    go test
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.2" data-path="../ch11/ch11-02.html">
            
                <a href="../ch11/ch11-02.html">
            
                    
                    测试函数
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.3" data-path="../ch11/ch11-03.html">
            
                <a href="../ch11/ch11-03.html">
            
                    
                    测试覆盖率
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.4" data-path="../ch11/ch11-04.html">
            
                <a href="../ch11/ch11-04.html">
            
                    
                    基准测试
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.5" data-path="../ch11/ch11-05.html">
            
                <a href="../ch11/ch11-05.html">
            
                    
                    剖析
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.6" data-path="../ch11/ch11-06.html">
            
                <a href="../ch11/ch11-06.html">
            
                    
                    示例函数
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.13" data-path="../ch12/ch12.html">
            
                <a href="../ch12/ch12.html">
            
                    
                    反射
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.13.1" data-path="../ch12/ch12-01.html">
            
                <a href="../ch12/ch12-01.html">
            
                    
                    为何需要反射?
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.2" data-path="../ch12/ch12-02.html">
            
                <a href="../ch12/ch12-02.html">
            
                    
                    reflect.Type和reflect.Value
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.3" data-path="../ch12/ch12-03.html">
            
                <a href="../ch12/ch12-03.html">
            
                    
                    Display递归打印
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.4" data-path="../ch12/ch12-04.html">
            
                <a href="../ch12/ch12-04.html">
            
                    
                    示例: 编码S表达式
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.5" data-path="../ch12/ch12-05.html">
            
                <a href="../ch12/ch12-05.html">
            
                    
                    通过reflect.Value修改值
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.6" data-path="../ch12/ch12-06.html">
            
                <a href="../ch12/ch12-06.html">
            
                    
                    示例: 解码S表达式
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.7" data-path="../ch12/ch12-07.html">
            
                <a href="../ch12/ch12-07.html">
            
                    
                    获取结构体字段标签
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.8" data-path="../ch12/ch12-08.html">
            
                <a href="../ch12/ch12-08.html">
            
                    
                    显示一个类型的方法集
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.9" data-path="../ch12/ch12-09.html">
            
                <a href="../ch12/ch12-09.html">
            
                    
                    几点忠告
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.14" data-path="../ch13/ch13.html">
            
                <a href="../ch13/ch13.html">
            
                    
                    底层编程
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.14.1" data-path="../ch13/ch13-01.html">
            
                <a href="../ch13/ch13-01.html">
            
                    
                    unsafe.Sizeof, Alignof 和 Offsetof
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.2" data-path="../ch13/ch13-02.html">
            
                <a href="../ch13/ch13-02.html">
            
                    
                    unsafe.Pointer
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.3" data-path="../ch13/ch13-03.html">
            
                <a href="../ch13/ch13-03.html">
            
                    
                    示例: 深度相等判断
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.4" data-path="../ch13/ch13-04.html">
            
                <a href="../ch13/ch13-04.html">
            
                    
                    通过cgo调用C代码
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.5" data-path="../ch13/ch13-05.html">
            
                <a href="../ch13/ch13-05.html">
            
                    
                    几点忠告
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.15" data-path="../appendix/appendix.html">
            
                <a href="../appendix/appendix.html">
            
                    
                    附录
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.15.1" data-path="../appendix/appendix-a-errata.html">
            
                <a href="../appendix/appendix-a-errata.html">
            
                    
                    附录A：原文勘误
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.15.2" data-path="../appendix/appendix-b-author.html">
            
                <a href="../appendix/appendix-b-author.html">
            
                    
                    附录B：作者译者
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.15.3" data-path="../appendix/appendix-c-cpoyright.html">
            
                <a href="../appendix/appendix-c-cpoyright.html">
            
                    
                    附录C：译文授权
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.15.4" data-path="../appendix/appendix-d-translations.html">
            
                <a href="../appendix/appendix-d-translations.html">
            
                    
                    附录D：其它语言
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    

    

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                                <h2 id="510-recover&#x6355;&#x83B7;&#x5F02;&#x5E38;">5.10. Recover&#x6355;&#x83B7;&#x5F02;&#x5E38;</h2>
<p>&#x901A;&#x5E38;&#x6765;&#x8BF4;&#xFF0C;&#x4E0D;&#x5E94;&#x8BE5;&#x5BF9;panic&#x5F02;&#x5E38;&#x505A;&#x4EFB;&#x4F55;&#x5904;&#x7406;&#xFF0C;&#x4F46;&#x6709;&#x65F6;&#xFF0C;&#x4E5F;&#x8BB8;&#x6211;&#x4EEC;&#x53EF;&#x4EE5;&#x4ECE;&#x5F02;&#x5E38;&#x4E2D;&#x6062;&#x590D;&#xFF0C;&#x81F3;&#x5C11;&#x6211;&#x4EEC;&#x53EF;&#x4EE5;&#x5728;&#x7A0B;&#x5E8F;&#x5D29;&#x6E83;&#x524D;&#xFF0C;&#x505A;&#x4E00;&#x4E9B;&#x64CD;&#x4F5C;&#x3002;&#x4E3E;&#x4E2A;&#x4F8B;&#x5B50;&#xFF0C;&#x5F53;web&#x670D;&#x52A1;&#x5668;&#x9047;&#x5230;&#x4E0D;&#x53EF;&#x9884;&#x6599;&#x7684;&#x4E25;&#x91CD;&#x95EE;&#x9898;&#x65F6;&#xFF0C;&#x5728;&#x5D29;&#x6E83;&#x524D;&#x5E94;&#x8BE5;&#x5C06;&#x6240;&#x6709;&#x7684;&#x8FDE;&#x63A5;&#x5173;&#x95ED;&#xFF1B;&#x5982;&#x679C;&#x4E0D;&#x505A;&#x4EFB;&#x4F55;&#x5904;&#x7406;&#xFF0C;&#x4F1A;&#x4F7F;&#x5F97;&#x5BA2;&#x6237;&#x7AEF;&#x4E00;&#x76F4;&#x5904;&#x4E8E;&#x7B49;&#x5F85;&#x72B6;&#x6001;&#x3002;&#x5982;&#x679C;web&#x670D;&#x52A1;&#x5668;&#x8FD8;&#x5728;&#x5F00;&#x53D1;&#x9636;&#x6BB5;&#xFF0C;&#x670D;&#x52A1;&#x5668;&#x751A;&#x81F3;&#x53EF;&#x4EE5;&#x5C06;&#x5F02;&#x5E38;&#x4FE1;&#x606F;&#x53CD;&#x9988;&#x5230;&#x5BA2;&#x6237;&#x7AEF;&#xFF0C;&#x5E2E;&#x52A9;&#x8C03;&#x8BD5;&#x3002;</p>
<p>&#x5982;&#x679C;&#x5728;deferred&#x51FD;&#x6570;&#x4E2D;&#x8C03;&#x7528;&#x4E86;&#x5185;&#x7F6E;&#x51FD;&#x6570;recover&#xFF0C;&#x5E76;&#x4E14;&#x5B9A;&#x4E49;&#x8BE5;defer&#x8BED;&#x53E5;&#x7684;&#x51FD;&#x6570;&#x53D1;&#x751F;&#x4E86;panic&#x5F02;&#x5E38;&#xFF0C;recover&#x4F1A;&#x4F7F;&#x7A0B;&#x5E8F;&#x4ECE;panic&#x4E2D;&#x6062;&#x590D;&#xFF0C;&#x5E76;&#x8FD4;&#x56DE;panic value&#x3002;&#x5BFC;&#x81F4;panic&#x5F02;&#x5E38;&#x7684;&#x51FD;&#x6570;&#x4E0D;&#x4F1A;&#x7EE7;&#x7EED;&#x8FD0;&#x884C;&#xFF0C;&#x4F46;&#x80FD;&#x6B63;&#x5E38;&#x8FD4;&#x56DE;&#x3002;&#x5728;&#x672A;&#x53D1;&#x751F;panic&#x65F6;&#x8C03;&#x7528;recover&#xFF0C;recover&#x4F1A;&#x8FD4;&#x56DE;nil&#x3002;</p>
<p>&#x8BA9;&#x6211;&#x4EEC;&#x4EE5;&#x8BED;&#x8A00;&#x89E3;&#x6790;&#x5668;&#x4E3A;&#x4F8B;&#xFF0C;&#x8BF4;&#x660E;recover&#x7684;&#x4F7F;&#x7528;&#x573A;&#x666F;&#x3002;&#x8003;&#x8651;&#x5230;&#x8BED;&#x8A00;&#x89E3;&#x6790;&#x5668;&#x7684;&#x590D;&#x6742;&#x6027;&#xFF0C;&#x5373;&#x4F7F;&#x67D0;&#x4E2A;&#x8BED;&#x8A00;&#x89E3;&#x6790;&#x5668;&#x76EE;&#x524D;&#x5DE5;&#x4F5C;&#x6B63;&#x5E38;&#xFF0C;&#x4E5F;&#x65E0;&#x6CD5;&#x80AF;&#x5B9A;&#x5B83;&#x6CA1;&#x6709;&#x6F0F;&#x6D1E;&#x3002;&#x56E0;&#x6B64;&#xFF0C;&#x5F53;&#x67D0;&#x4E2A;&#x5F02;&#x5E38;&#x51FA;&#x73B0;&#x65F6;&#xFF0C;&#x6211;&#x4EEC;&#x4E0D;&#x4F1A;&#x9009;&#x62E9;&#x8BA9;&#x89E3;&#x6790;&#x5668;&#x5D29;&#x6E83;&#xFF0C;&#x800C;&#x662F;&#x4F1A;&#x5C06;panic&#x5F02;&#x5E38;&#x5F53;&#x4F5C;&#x666E;&#x901A;&#x7684;&#x89E3;&#x6790;&#x9519;&#x8BEF;&#xFF0C;&#x5E76;&#x9644;&#x52A0;&#x989D;&#x5916;&#x4FE1;&#x606F;&#x63D0;&#x9192;&#x7528;&#x6237;&#x62A5;&#x544A;&#x6B64;&#x9519;&#x8BEF;&#x3002;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">func</span> Parse(input <span class="hljs-keyword">string</span>) (s *Syntax, err error) {
    <span class="hljs-keyword">defer</span> <span class="hljs-keyword">func</span>() {
        <span class="hljs-keyword">if</span> p := <span class="hljs-built_in">recover</span>(); p != <span class="hljs-literal">nil</span> {
            err = fmt.Errorf(<span class="hljs-string">&quot;internal error: %v&quot;</span>, p)
        }
    }()
    <span class="hljs-comment">// ...parser...</span>
}
</code></pre>
<p>deferred&#x51FD;&#x6570;&#x5E2E;&#x52A9;Parse&#x4ECE;panic&#x4E2D;&#x6062;&#x590D;&#x3002;&#x5728;deferred&#x51FD;&#x6570;&#x5185;&#x90E8;&#xFF0C;panic value&#x88AB;&#x9644;&#x52A0;&#x5230;&#x9519;&#x8BEF;&#x4FE1;&#x606F;&#x4E2D;&#xFF1B;&#x5E76;&#x7528;err&#x53D8;&#x91CF;&#x63A5;&#x6536;&#x9519;&#x8BEF;&#x4FE1;&#x606F;&#xFF0C;&#x8FD4;&#x56DE;&#x7ED9;&#x8C03;&#x7528;&#x8005;&#x3002;&#x6211;&#x4EEC;&#x4E5F;&#x53EF;&#x4EE5;&#x901A;&#x8FC7;&#x8C03;&#x7528;runtime.Stack&#x5F80;&#x9519;&#x8BEF;&#x4FE1;&#x606F;&#x4E2D;&#x6DFB;&#x52A0;&#x5B8C;&#x6574;&#x7684;&#x5806;&#x6808;&#x8C03;&#x7528;&#x4FE1;&#x606F;&#x3002;</p>
<p>&#x4E0D;&#x52A0;&#x533A;&#x5206;&#x7684;&#x6062;&#x590D;&#x6240;&#x6709;&#x7684;panic&#x5F02;&#x5E38;&#xFF0C;&#x4E0D;&#x662F;&#x53EF;&#x53D6;&#x7684;&#x505A;&#x6CD5;&#xFF1B;&#x56E0;&#x4E3A;&#x5728;panic&#x4E4B;&#x540E;&#xFF0C;&#x65E0;&#x6CD5;&#x4FDD;&#x8BC1;&#x5305;&#x7EA7;&#x53D8;&#x91CF;&#x7684;&#x72B6;&#x6001;&#x4ECD;&#x7136;&#x548C;&#x6211;&#x4EEC;&#x9884;&#x671F;&#x4E00;&#x81F4;&#x3002;&#x6BD4;&#x5982;&#xFF0C;&#x5BF9;&#x6570;&#x636E;&#x7ED3;&#x6784;&#x7684;&#x4E00;&#x6B21;&#x91CD;&#x8981;&#x66F4;&#x65B0;&#x6CA1;&#x6709;&#x88AB;&#x5B8C;&#x6574;&#x5B8C;&#x6210;&#x3001;&#x6587;&#x4EF6;&#x6216;&#x8005;&#x7F51;&#x7EDC;&#x8FDE;&#x63A5;&#x6CA1;&#x6709;&#x88AB;&#x5173;&#x95ED;&#x3001;&#x83B7;&#x5F97;&#x7684;&#x9501;&#x6CA1;&#x6709;&#x88AB;&#x91CA;&#x653E;&#x3002;&#x6B64;&#x5916;&#xFF0C;&#x5982;&#x679C;&#x5199;&#x65E5;&#x5FD7;&#x65F6;&#x4EA7;&#x751F;&#x7684;panic&#x88AB;&#x4E0D;&#x52A0;&#x533A;&#x5206;&#x7684;&#x6062;&#x590D;&#xFF0C;&#x53EF;&#x80FD;&#x4F1A;&#x5BFC;&#x81F4;&#x6F0F;&#x6D1E;&#x88AB;&#x5FFD;&#x7565;&#x3002;</p>
<p>&#x867D;&#x7136;&#x628A;&#x5BF9;panic&#x7684;&#x5904;&#x7406;&#x90FD;&#x96C6;&#x4E2D;&#x5728;&#x4E00;&#x4E2A;&#x5305;&#x4E0B;&#xFF0C;&#x6709;&#x52A9;&#x4E8E;&#x7B80;&#x5316;&#x5BF9;&#x590D;&#x6742;&#x548C;&#x4E0D;&#x53EF;&#x4EE5;&#x9884;&#x6599;&#x95EE;&#x9898;&#x7684;&#x5904;&#x7406;&#xFF0C;&#x4F46;&#x4F5C;&#x4E3A;&#x88AB;&#x5E7F;&#x6CDB;&#x9075;&#x5B88;&#x7684;&#x89C4;&#x8303;&#xFF0C;&#x4F60;&#x4E0D;&#x5E94;&#x8BE5;&#x8BD5;&#x56FE;&#x53BB;&#x6062;&#x590D;&#x5176;&#x4ED6;&#x5305;&#x5F15;&#x8D77;&#x7684;panic&#x3002;&#x516C;&#x6709;&#x7684;API&#x5E94;&#x8BE5;&#x5C06;&#x51FD;&#x6570;&#x7684;&#x8FD0;&#x884C;&#x5931;&#x8D25;&#x4F5C;&#x4E3A;error&#x8FD4;&#x56DE;&#xFF0C;&#x800C;&#x4E0D;&#x662F;panic&#x3002;&#x540C;&#x6837;&#x7684;&#xFF0C;&#x4F60;&#x4E5F;&#x4E0D;&#x5E94;&#x8BE5;&#x6062;&#x590D;&#x4E00;&#x4E2A;&#x7531;&#x4ED6;&#x4EBA;&#x5F00;&#x53D1;&#x7684;&#x51FD;&#x6570;&#x5F15;&#x8D77;&#x7684;panic&#xFF0C;&#x6BD4;&#x5982;&#x8BF4;&#x8C03;&#x7528;&#x8005;&#x4F20;&#x5165;&#x7684;&#x56DE;&#x8C03;&#x51FD;&#x6570;&#xFF0C;&#x56E0;&#x4E3A;&#x4F60;&#x65E0;&#x6CD5;&#x786E;&#x4FDD;&#x8FD9;&#x6837;&#x505A;&#x662F;&#x5B89;&#x5168;&#x7684;&#x3002;</p>
<p>&#x6709;&#x65F6;&#x6211;&#x4EEC;&#x5F88;&#x96BE;&#x5B8C;&#x5168;&#x9075;&#x5FAA;&#x89C4;&#x8303;&#xFF0C;&#x4E3E;&#x4E2A;&#x4F8B;&#x5B50;&#xFF0C;net/http&#x5305;&#x4E2D;&#x63D0;&#x4F9B;&#x4E86;&#x4E00;&#x4E2A;web&#x670D;&#x52A1;&#x5668;&#xFF0C;&#x5C06;&#x6536;&#x5230;&#x7684;&#x8BF7;&#x6C42;&#x5206;&#x53D1;&#x7ED9;&#x7528;&#x6237;&#x63D0;&#x4F9B;&#x7684;&#x5904;&#x7406;&#x51FD;&#x6570;&#x3002;&#x5F88;&#x663E;&#x7136;&#xFF0C;&#x6211;&#x4EEC;&#x4E0D;&#x80FD;&#x56E0;&#x4E3A;&#x67D0;&#x4E2A;&#x5904;&#x7406;&#x51FD;&#x6570;&#x5F15;&#x53D1;&#x7684;panic&#x5F02;&#x5E38;&#xFF0C;&#x6740;&#x6389;&#x6574;&#x4E2A;&#x8FDB;&#x7A0B;&#xFF1B;web&#x670D;&#x52A1;&#x5668;&#x9047;&#x5230;&#x5904;&#x7406;&#x51FD;&#x6570;&#x5BFC;&#x81F4;&#x7684;panic&#x65F6;&#x4F1A;&#x8C03;&#x7528;recover&#xFF0C;&#x8F93;&#x51FA;&#x5806;&#x6808;&#x4FE1;&#x606F;&#xFF0C;&#x7EE7;&#x7EED;&#x8FD0;&#x884C;&#x3002;&#x8FD9;&#x6837;&#x7684;&#x505A;&#x6CD5;&#x5728;&#x5B9E;&#x8DF5;&#x4E2D;&#x5F88;&#x4FBF;&#x6377;&#xFF0C;&#x4F46;&#x4E5F;&#x4F1A;&#x5F15;&#x8D77;&#x8D44;&#x6E90;&#x6CC4;&#x6F0F;&#xFF0C;&#x6216;&#x662F;&#x56E0;&#x4E3A;recover&#x64CD;&#x4F5C;&#xFF0C;&#x5BFC;&#x81F4;&#x5176;&#x4ED6;&#x95EE;&#x9898;&#x3002;</p>
<p>&#x57FA;&#x4E8E;&#x4EE5;&#x4E0A;&#x539F;&#x56E0;&#xFF0C;&#x5B89;&#x5168;&#x7684;&#x505A;&#x6CD5;&#x662F;&#x6709;&#x9009;&#x62E9;&#x6027;&#x7684;recover&#x3002;&#x6362;&#x53E5;&#x8BDD;&#x8BF4;&#xFF0C;&#x53EA;&#x6062;&#x590D;&#x5E94;&#x8BE5;&#x88AB;&#x6062;&#x590D;&#x7684;panic&#x5F02;&#x5E38;&#xFF0C;&#x6B64;&#x5916;&#xFF0C;&#x8FD9;&#x4E9B;&#x5F02;&#x5E38;&#x6240;&#x5360;&#x7684;&#x6BD4;&#x4F8B;&#x5E94;&#x8BE5;&#x5C3D;&#x53EF;&#x80FD;&#x7684;&#x4F4E;&#x3002;&#x4E3A;&#x4E86;&#x6807;&#x8BC6;&#x67D0;&#x4E2A;panic&#x662F;&#x5426;&#x5E94;&#x8BE5;&#x88AB;&#x6062;&#x590D;&#xFF0C;&#x6211;&#x4EEC;&#x53EF;&#x4EE5;&#x5C06;panic value&#x8BBE;&#x7F6E;&#x6210;&#x7279;&#x6B8A;&#x7C7B;&#x578B;&#x3002;&#x5728;recover&#x65F6;&#x5BF9;panic value&#x8FDB;&#x884C;&#x68C0;&#x67E5;&#xFF0C;&#x5982;&#x679C;&#x53D1;&#x73B0;panic value&#x662F;&#x7279;&#x6B8A;&#x7C7B;&#x578B;&#xFF0C;&#x5C31;&#x5C06;&#x8FD9;&#x4E2A;panic&#x4F5C;&#x4E3A;error&#x5904;&#x7406;&#xFF0C;&#x5982;&#x679C;&#x4E0D;&#x662F;&#xFF0C;&#x5219;&#x6309;&#x7167;&#x6B63;&#x5E38;&#x7684;panic&#x8FDB;&#x884C;&#x5904;&#x7406;&#xFF08;&#x5728;&#x4E0B;&#x9762;&#x7684;&#x4F8B;&#x5B50;&#x4E2D;&#xFF0C;&#x6211;&#x4EEC;&#x4F1A;&#x770B;&#x5230;&#x8FD9;&#x79CD;&#x65B9;&#x5F0F;&#xFF09;&#x3002;</p>
<p>&#x4E0B;&#x9762;&#x7684;&#x4F8B;&#x5B50;&#x662F;title&#x51FD;&#x6570;&#x7684;&#x53D8;&#x5F62;&#xFF0C;&#x5982;&#x679C;HTML&#x9875;&#x9762;&#x5305;&#x542B;&#x591A;&#x4E2A;<code>&lt;title&gt;</code>&#xFF0C;&#x8BE5;&#x51FD;&#x6570;&#x4F1A;&#x7ED9;&#x8C03;&#x7528;&#x8005;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x9519;&#x8BEF;&#xFF08;error&#xFF09;&#x3002;&#x5728;soleTitle&#x5185;&#x90E8;&#x5904;&#x7406;&#x65F6;&#xFF0C;&#x5982;&#x679C;&#x68C0;&#x6D4B;&#x5230;&#x6709;&#x591A;&#x4E2A;<code>&lt;title&gt;</code>&#xFF0C;&#x4F1A;&#x8C03;&#x7528;panic&#xFF0C;&#x963B;&#x6B62;&#x51FD;&#x6570;&#x7EE7;&#x7EED;&#x9012;&#x5F52;&#xFF0C;&#x5E76;&#x5C06;&#x7279;&#x6B8A;&#x7C7B;&#x578B;bailout&#x4F5C;&#x4E3A;panic&#x7684;&#x53C2;&#x6570;&#x3002;</p>
<pre><code class="lang-Go"><span class="hljs-comment">// soleTitle returns the text of the first non-empty title element</span>
<span class="hljs-comment">// in doc, and an error if there was not exactly one.</span>
<span class="hljs-keyword">func</span> soleTitle(doc *html.Node) (title <span class="hljs-keyword">string</span>, err error) {
    <span class="hljs-keyword">type</span> bailout <span class="hljs-keyword">struct</span>{}
    <span class="hljs-keyword">defer</span> <span class="hljs-keyword">func</span>() {
        <span class="hljs-keyword">switch</span> p := <span class="hljs-built_in">recover</span>(); p {
        <span class="hljs-keyword">case</span> <span class="hljs-literal">nil</span>:       <span class="hljs-comment">// no panic</span>
        <span class="hljs-keyword">case</span> bailout{}: <span class="hljs-comment">// &quot;expected&quot; panic</span>
            err = fmt.Errorf(<span class="hljs-string">&quot;multiple title elements&quot;</span>)
        <span class="hljs-keyword">default</span>:
            <span class="hljs-built_in">panic</span>(p) <span class="hljs-comment">// unexpected panic; carry on panicking</span>
        }
    }()
    <span class="hljs-comment">// Bail out of recursion if we find more than one nonempty title.</span>
    forEachNode(doc, <span class="hljs-keyword">func</span>(n *html.Node) {
        <span class="hljs-keyword">if</span> n.Type == html.ElementNode &amp;&amp; n.Data == <span class="hljs-string">&quot;title&quot;</span> &amp;&amp;
            n.FirstChild != <span class="hljs-literal">nil</span> {
            <span class="hljs-keyword">if</span> title != <span class="hljs-string">&quot;&quot;</span> {
                <span class="hljs-built_in">panic</span>(bailout{}) <span class="hljs-comment">// multiple titleelements</span>
            }
            title = n.FirstChild.Data
        }
    }, <span class="hljs-literal">nil</span>)
    <span class="hljs-keyword">if</span> title == <span class="hljs-string">&quot;&quot;</span> {
        <span class="hljs-keyword">return</span> <span class="hljs-string">&quot;&quot;</span>, fmt.Errorf(<span class="hljs-string">&quot;no title element&quot;</span>)
    }
    <span class="hljs-keyword">return</span> title, <span class="hljs-literal">nil</span>
}
</code></pre>
<p>&#x5728;&#x4E0A;&#x4F8B;&#x4E2D;&#xFF0C;deferred&#x51FD;&#x6570;&#x8C03;&#x7528;recover&#xFF0C;&#x5E76;&#x68C0;&#x67E5;panic value&#x3002;&#x5F53;panic value&#x662F;bailout{}&#x7C7B;&#x578B;&#x65F6;&#xFF0C;deferred&#x51FD;&#x6570;&#x751F;&#x6210;&#x4E00;&#x4E2A;error&#x8FD4;&#x56DE;&#x7ED9;&#x8C03;&#x7528;&#x8005;&#x3002;&#x5F53;panic value&#x662F;&#x5176;&#x4ED6;non-nil&#x503C;&#x65F6;&#xFF0C;&#x8868;&#x793A;&#x53D1;&#x751F;&#x4E86;&#x672A;&#x77E5;&#x7684;panic&#x5F02;&#x5E38;&#xFF0C;deferred&#x51FD;&#x6570;&#x5C06;&#x8C03;&#x7528;panic&#x51FD;&#x6570;&#x5E76;&#x5C06;&#x5F53;&#x524D;&#x7684;panic value&#x4F5C;&#x4E3A;&#x53C2;&#x6570;&#x4F20;&#x5165;&#xFF1B;&#x6B64;&#x65F6;&#xFF0C;&#x7B49;&#x540C;&#x4E8E;recover&#x6CA1;&#x6709;&#x505A;&#x4EFB;&#x4F55;&#x64CD;&#x4F5C;&#x3002;&#xFF08;&#x8BF7;&#x6CE8;&#x610F;&#xFF1A;&#x5728;&#x4F8B;&#x5B50;&#x4E2D;&#xFF0C;&#x5BF9;&#x53EF;&#x9884;&#x671F;&#x7684;&#x9519;&#x8BEF;&#x91C7;&#x7528;&#x4E86;panic&#xFF0C;&#x8FD9;&#x8FDD;&#x53CD;&#x4E86;&#x4E4B;&#x524D;&#x7684;&#x5EFA;&#x8BAE;&#xFF0C;&#x6211;&#x4EEC;&#x5728;&#x6B64;&#x53EA;&#x662F;&#x60F3;&#x5411;&#x8BFB;&#x8005;&#x6F14;&#x793A;&#x8FD9;&#x79CD;&#x673A;&#x5236;&#x3002;&#xFF09;</p>
<p>&#x6709;&#x4E9B;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x6211;&#x4EEC;&#x65E0;&#x6CD5;&#x6062;&#x590D;&#x3002;&#x67D0;&#x4E9B;&#x81F4;&#x547D;&#x9519;&#x8BEF;&#x4F1A;&#x5BFC;&#x81F4;Go&#x5728;&#x8FD0;&#x884C;&#x65F6;&#x7EC8;&#x6B62;&#x7A0B;&#x5E8F;&#xFF0C;&#x5982;&#x5185;&#x5B58;&#x4E0D;&#x8DB3;&#x3002;</p>
<p><strong>&#x7EC3;&#x4E60;5.19&#xFF1A;</strong> &#x4F7F;&#x7528;panic&#x548C;recover&#x7F16;&#x5199;&#x4E00;&#x4E2A;&#x4E0D;&#x5305;&#x542B;return&#x8BED;&#x53E5;&#x4F46;&#x80FD;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x975E;&#x96F6;&#x503C;&#x7684;&#x51FD;&#x6570;&#x3002;</p>

                                
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